In cooling systems for liquid-cooled internal combustion engines, it has become common practice to utilize accumulator tanks for accumulating and returning make-up coolant to the radiator of the vehicle in which the engine is installed. In addition, such systems generally provide for an automatic positive anti-aeration system to eliminate entrapped air and other gasses from the liquid coolant, thereby increasing the efficiency of the cooling system associated with the engine.
Typical systems for accomplishing the above results are illustrated in the patents to Walter C. Avrea, No. RE 27,965, and No. 4,006,775. The system disclosed in the '965 reissue patent includes a plastic bottle forming a coolant reservoir and coolant overflow accumulator. This bottle is located in a position in the vehicle generally alongside the radiator. A specially constructed radiator cap having a two-way check valve replaces the conventional radiator cap and a length of tubing extends from the radiator cap overflow outlet to the reservoir bottle. When the pressure in the cooling system exceeds a pre-established amount, the first check valve in the radiator cap opens to allow air and coolant to escape into the reservoir bottle. Upon cool-down of the system, the other check valve in the cap opens in response to the vacuum condition created in the vehicle cooling system to withdraw fluid from the bottle and return it to the engine cooling system.
A primary disadvantage in this system is the necessity of the special radiator cap requiring the built-in, two-way check valve or two separate check valves. In addition, if there is a leak somewhere in the vehicle cooling system which breaks the vacuum upon cool-down of the system, coolant liquid is not withdrawn from the reservoir bottle since the necessary vacuum to open the check valve and cause this to occur is not present. Consequently, it is possible for a user of the system to check the reservoir bottle, see that it is full of fluid, and mistakenly believe that the cooling system for the engine is full of liquid coolant when, in fact, it could be dangerously low in coolant.
The Avrea patent, No. 4,006,775, is a modification of the system shown in the '965 reissue patent. In the '775 patent, the special radiator valve is not employed. Instead, the radiator is constructed either as a unitary device or with a separate accumulator tank alongside the radiator to permit overflow through a first check valve into the accumulator and return through a second check valve (which may be a gravity-opened check valve) at the bottom of the radiator, communicating in a passageway between the bottom of the accumulator tank and the bottom of the radiator. The system of the '775 patent eliminates the necessity for the special radiator cap. The system disclosed, however, still is subject to the disadvantage that it is possible for liquid to appear in the accumulator tank above the bottom passageway and still have a dangerously low coolant level in the vehicle cooling system, including the engine and radiator.
Other prior art systems for removing air and other gasses from the coolant in the vehicle cooling system are disclosed in the patents to Pabst, No. 4,064,848 and 4,175,616. In the Pabst system, a separate equalization tank (either independent or built in as the upper portion of the vehicle radiator) is utilized with baffles for separating the air bubbles in the coolant supplied to the tank from coolant returning from the tank and returned to the vehicle cooling system. A single tank is employed, and there is no separate pressure check valve to admit fluid into the tank or to permit fluid to return from the tank to the vehicle cooling system. Gasses are simply accumulated near the top of the tank, which necessarily must be a pressurized tank to maintain the cooling system pressure necessary for its proper operation. Consequently, the systems disclosed in the Pabst patents are less effective than the systems disclosed in the Avrea patents for removing accumulated air and other gasses from the cooling system.
A major shortcoming in any coolant recovery system utilizing a vacuum return for pulling fluid from the accumulator back into the vehicle cooling system or radiator is that if there is a leak in the cooling system for the vehicle, such as caused by a leaky heater hose or any of the radiator hoses, no vacuum is created when the engine cools down. Air then is drawn into the main system through the leak. Consequently, coolant remains in the recovery bottle and frequently, the owner, checking the coolant in the recovery bottle, assumes that coolant is in the engine in sufficient quantities when this is not the case.
In systems of the type shown in the Pabst patents, the effective separation of gasses from the liquid coolant which is achieved by the Avrea patents is not present. The equalization tanks of Pabst are located above the radiator; so that if there is a leak in the vehicle cooling system, the fluid in the tanks will flow into the system, even if no vacuum is present. While this overcomes one of the disadvantages of the Avrea systems, the effective separation of air and gasses from the liquid coolant of Avrea is not accomplished by the Pabst systems.
Accordingly, it is desirable to provide a coolant recovery system for use with liquid-cooled internal combustion engines and the associated cooling radiator used in cooling systems for such engines which is not subject to the aforementioned disadvantages but which incorporates positive and effective coolant recovery and positive anti-aeration of the liquid coolant in the cooling system for the vehicle.